Flow rate control valve for construction machine

ABSTRACT

Disclosed is a flow rate control valve for a construction machine. A flow rate control valve for a construction machine comprises: a valve body having a pump channel for receiving operating oil from a hydraulic pump, a supply channel connected to the pump channel, and an actuator port connected to a hydraulic actuator; a spool installed inside the valve body to be switchable such that, when switched in response to application of signal pressure, the spool selectively causes the supply channel and the actuator port to communicate with each other; a tank channel installed inside the valve body and connected to an operating oil tank; and an orifice formed in the spool to have an inlet formed on an end and an outlet communicating with the tank channel, wherein, when the spool is initially actuated, a part of the signal pressure is discharged to the operating oil tank via the orifice.

TECHNICAL FIELD

The present invention relates to a flow rate control valve for aconstruction machine. More particularly, the present invention relatesto such a flow rate control valve for a construction machine, which cancontrol hydraulic fluid supplied from a hydraulic pump to a hydraulicactuator.

BACKGROUND OF THE INVENTION

Referring to FIGS. 1 to 3, in accordance with an embodiment of the priorart, there is shown a flow rate control valve 3 for a constructionmachine, which is configured to control hydraulic fluid supplied from ahydraulic pump 1 to a hydraulic actuator 2 (e.g., boom cylinder) when aspool is shifted in response to a signal pressure applied thereto from aremote control valve (RCV) A.

The flow rate control valve for a construction machine includes:

-   -   a valve body 9 that includes a pump path 4 to which hydraulic        fluid from a hydraulic pump 1 is supplied, a supply path 6        connected to the pump path 4, and actuator ports 7 and 8        connected to a hydraulic actuator 2;    -   a spool 10 that is installed in the valve body 9 and is shifted        in response to the signal pressure applied thereto to cause the        supply path 6 and the actuator port 7 or 8 to fluidically        communicate with each other selectively; and    -   a tank path 11 that is formed in the valve body 9 and is        connected to a hydraulic fluid tank T so that the hydraulic        fluid from the hydraulic pump 1 is supplied to the hydraulic        actuator 2 through the actuator port 7 at one side of the valve        body 9 and hydraulic fluid discharged from the hydraulic        actuator 2 is returned to the hydraulic fluid tank T through the        actuator port 8 at the other side of the valve body 9 in        response to the shift of the spool 10.

When a signal pressure from the remote control valve A is applied to asignal pressure port at a left side of the valve body 9 to cause thespool 10 to be shifted to the right on the drawing sheet, the hydraulicfluid from the hydraulic pump 1 is supplied to the hydraulic actuator 2via the pump path 4, the supply path 6, a notch 10 a of the spool 10,and the actuator port 7 in this order.

Simultaneously, the hydraulic fluid discharged from the hydraulicactuator 2 is returned to the hydraulic fluid tank T via the actuatorport 8, a notch 10 b of the spool 10, and the tank path 11 in thisorder.

Thus, the hydraulic actuator 2 can be driven in a stretchable manner toperform a boom-up operation.

The flow rate control valve 3 in accordance with the prior art allowsthe spool 10 to be shifted in response to the signal pressure applied tothe spool by the manipulation of the remote control valve A to controlthe hydraulic fluid supplied from the hydraulic pump 1 to the hydraulicactuator 2 and operate the work apparatus such as a boom, an arm, or abucket through the drive of the hydraulic actuator 2.

In this case, the remote control valve A is manipulated by using anoperator's hand or foot, and thus there is a limitation in finely andsmoothly manipulating the remote control valve A to the extent to whichthe operator desires. For example, this is the case where the remotecontrol valve A is manipulated in an initial stage to initiate theleveling work in a state in which the work apparatus 5 is stretched tothe maximum.

As shown in FIGS. 2 and 3, in the case of the leveling work, an armmanipulation amount (i.e., in an arm-in or arm-out operation) isrelatively larger than a boom manipulation amount (i.e., in a boom-up orboom-down operation).

As described above, even in the case where the manipulation amount ofthe hydraulic actuator 2 is small, a displacement amount at a distal endof the bucket where the leveling work is actually carried out isincreased due to a length L of the work apparatus 5. In other words,even in the case where the hydraulic actuator 2 is unstably manipulatedin a significantly small manipulation amount, the distal end of thebucket is moved sensitively moved, thus resulting in a problem in thatthe leveling work cannot be smoothly performed.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve theaforementioned problems occurring in the prior art, and it is an objectof the present invention to provide a flow rate control valve for aconstruction machine, in which a spool of the flow rate control valvethat controls hydraulic fluid supplied to a work apparatus is preventedfrom being excessively manipulated in an initial stage of the operationof the spool, and a shock can be prevented from occurring in the workapparatus due to the sudden shift of the spool at the initial operationstage of the spool.

TECHNICAL SOLUTION

To achieve the above object, in accordance with an embodiment of thepresent invention, there is provided a flow rate control valve for aconstruction machine, including:

-   -   a valve body including a pump path to which hydraulic fluid from        a hydraulic pump is supplied, a supply path connected to the        pump path, and actuator ports connected to a hydraulic actuator;    -   a spool installed in the valve body and shifted in response to a        signal pressure applied thereto to cause the supply path and the        actuator port to fluidically communicate with each other        selectively;    -   a tank path installed in the valve body and connected to a        hydraulic fluid tank; and    -   an orifice formed in the spool, the orifice including an inlet        formed at an end portion to which the signal pressure is applied        and an outlet formed to fluidically communicate with the tank        path,    -   wherein part of the signal pressure is discharged to the        hydraulic fluid tank through the orifice at an initial stage of        the operation of the spool.

In the flow rate control valve, the hydraulic actuator may include atleast one of a boom cylinder, an arm cylinder, and a bucket cylinder.

In the flow rate control valve, the outlet 13 of the orifice may beformed at a position that is spaced apart by a predetermined distancefrom the end portion of the spool to which the signal pressure isapplied so that the orifice is closed after the spool is moved over apredetermined distance in response to the signal pressure appliedthereto.

In the flow rate control valve, the orifice may be formed at at leastone of both ends of the spool.

ADVANTAGEOUS EFFECT

The flow rate control valve for a construction machine in accordancewith the present invention as constructed above has the followingadvantages.

The excessive manipulation of the spool of the flow rate control valvecan be avoided at the initial stage of the operation of the spool. Inaddition, a shock can be prevented from occurring in the work apparatusdue to the sudden shift of the spool.

Moreover, the shock occurring at the initial stage of the operation ofthe spool of the flow rate control valve is minimized so that the workapparatus can be performed smoothly, thereby improving the workabilityduring the leveling work using an excavator and relieving an operator'sfatigue.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, other features and advantages of the presentinvention will become more apparent by describing the preferredembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic view showing a neutral state of a spool in aflow rate control valve for a construction machine in accordance withthe prior art;

FIG. 2 is a diagrammatic view showing an initial stage of the operationof the spool in the flow rate control valve shown in FIG. 1;

FIG. 3 is an enlarged view showing main elements of the flow ratecontrol valve in initial stage of the operation of the spool shown inFIG. 2;

FIG. 4 is a diagrammatic view showing a neutral state of a spool in aflow rate control valve for a construction machine in accordance with apreferred embodiment of the present invention;

FIG. 5 is a diagrammatic view showing an initial stage of the operationof the spool in the flow rate control valve shown in FIG. 4;

FIG. 6 is an enlarged view showing main elements of the flow ratecontrol valve in initial stage of the operation of the spool shown inFIG. 5;

FIG. 7 is a diagrammatic view showing a state in which the spool ismoved over a predetermined distance in the flow rate control valve shownin FIG. 4; and

FIG. 8 is an enlarged view showing main elements of the flow ratecontrol valve in which the spool shown in FIG. 7 is moved over apredetermined distance.

EXPLANATION ON REFERENCE NUMERALS OF MAIN ELEMENTS IN THE DRAWINGS

1: hydraulic pump

2: hydraulic actuator

3: flow rate control valve

4: pump path

5: work apparatus

6: supply path

7, 8: actuator port

9: valve body

10: spool

11: tank path

12: inlet

13: outlet

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a flow rate control valve for a construction machine inaccordance with a preferred embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings. Thematters defined in the description, such as the detailed constructionand elements, are nothing but specific details provided to assist thoseof ordinary skill in the art in a comprehensive understanding of theinvention, and the present invention is not limited to the embodimentsdisclosed hereinafter.

In order to definitely describe the present invention, a portion havingno relevant to the description will be omitted, and through thespecification, like elements are designated by like reference numerals.

In the specification and the claims, when a portion includes an element,it is meant to include other elements, but not exclude the otherelements unless otherwise specifically stated herein.

FIG. 4 is a diagrammatic view showing a neutral state of a spool in aflow rate control valve for a construction machine in accordance with apreferred embodiment of the present invention, FIG. 5 is a diagrammaticview showing an initial stage of the operation of the spool in the flowrate control valve shown in FIG. 4, FIG. 6 is an enlarged view showingmain elements of the flow rate control valve in initial stage of theoperation of the spool shown in FIG. 5, FIG. 7 is a diagrammatic viewshowing a state in which the spool is moved over a predetermineddistance in the flow rate control valve shown in FIG. 4, and FIG. 8 isan enlarged view showing main elements of the flow rate control valve inwhich the spool shown in FIG. 7 is moved over a predetermined distance.

Referring to FIGS. 4 to 8, in accordance with an embodiment of thepresent invention, there is shown a flow rate control valve 3 for aconstruction machine, which is configured to control hydraulic fluidsupplied from a hydraulic pump 1 to a hydraulic actuator 2 when a spoolis shifted in response to a signal pressure applied thereto from aremote control valve (RCV) A.

The flow rate control valve 3 for a construction machine includes:

-   -   a valve body 9 that includes a pump path 4 to which the        hydraulic fluid from the hydraulic pump 1 is supplied, a supply        path 6 connected to the pump path 4, and actuator ports 7 and 8        connected to a hydraulic actuator 2;    -   a spool 10 that is installed in the valve body 9 and is shifted        in response to the signal pressure applied thereto to cause the        supply path 6 and the actuator port 7 or 8 to fluidically        communicate with each other selectively;    -   a tank path 11 that is installed in the valve body 9 and is        connected to a hydraulic fluid tank T so that the hydraulic        fluid from the hydraulic pump 1 is supplied to the hydraulic        actuator 2 through the actuator port 7 at one side of the valve        body 9 and hydraulic fluid discharged from the hydraulic        actuator 2 is returned to the hydraulic fluid tank T through the        actuator port 8 at the other side of the valve body 9 in        response to the shift of the spool 10; and    -   an orifice 14 that is formed in the spool, the orifice including        an inlet 12 formed at an end portion to which the signal        pressure is applied and an outlet 13 formed to fluidically        communicate with the hydraulic fluid tank T,    -   wherein part of the signal pressure is discharged to the        hydraulic fluid tank T through the orifice 14 at an initial        stage of the operation of the spool 10.

The hydraulic actuator 2 is at least one of a boom cylinder, an armcylinder, and a bucket cylinder.

The outlet 13 of the orifice 14 is formed at a position that is spacedapart by a predetermined distance from the end portion of the spool 10to which the signal pressure is applied so that the orifice 14 is closedafter the spool 10 is moved over a predetermined distance in response tothe signal pressure applied thereto.

The orifice 14 is formed at at least one of both ends of the spool 10.

For example, in the drawings, the orifice 14 is formed at a left end ofthe spool 10.

According to the configuration as described above, as shown in FIG. 4, alever of the remote control valve A is held in a neutral position, andthus the spool 10 of the flow rate control valve 3 is also held in aneutral position. For this reason, because the supply path 6 is blockedfrom fluidically communicating with the pump path 4 to which thehydraulic fluid from the hydraulic pump 1 is supplied, the hydraulicfluid is not supplied to the hydraulic actuator 2.

As shown in FIGS. 5 and 6, when the lever of the remote control valve Ais manipulated to the right on the drawing sheet, the signal pressure isapplied to a signal pressure port at a left side of the flow ratecontrol valve 3 to press a left end of the spool 10 to cause the spoolto be shifted to the right on the drawing sheet. The hydraulic fluidfrom the hydraulic pump is supplied to the hydraulic actuator 2 via thepump path 4, the supply path 6, a notch 10 a of the spool 10, and theactuator port 7 in this order in response to the shift of the spool 10.In this case, the hydraulic fluid discharged from the hydraulic actuator2 is returned to the hydraulic fluid tank T via the actuator port 8, anotch 10 b of the spool 10, and the tank path 11 in this order. Thus,the hydraulic actuator 2 can be driven in a stretchable manner toperform a boom-up operation.

By virtue of the manipulation of the remote control valve, part of thesignal pressure applied to the signal pressure port of the valve body 9shifts the spool 10 to cause the hydraulic fluid from the hydraulic pumpto be supplied to the hydraulic actuator 2, and part of the signalpressure is introduced into the spool 10 through the inlet 12 of theorifice 14 formed at the end portion of the spool 10 and then is bled tothe hydraulic fluid tank T through the outlet 13 of the orifice 14.

In other words, part of the signal pressure applied from the remotecontrol valve A to the spool 10 is bled to the hydraulic fluid tank Tthrough the orifice 14 so that the sudden operation of the spool 10 canbe prevented at the initial operation stage of the spool 10. Thus, theshock or the sudden operation of the hydraulic actuator 2 is prevented,and thus the work apparatus 5 can be operated smoothly.

As shown in FIGS. 7 and 8, when the signal pressure is applied to thespool 10 by the manipulation of the remote control valve A, the spool 10is shifted over a predetermined distance to cause the orifice 14 to beclosed. In other words, the outlet 13 of the orifice 14 is closed by theinner periphery of the valve body 9, which corresponds to the outerperiphery of the spool 10. For this reason, it is possible to prevent anunnecessary loss of flow rate that occurs when the signal pressureapplied to the valve body 9 is drained to the hydraulic fluid tank T bythe manipulation of the remote control valve A

INDUSTRIAL APPLICABILITY

In accordance with the flow rate control valve for a constructionmachine of the present invention as constructed above, the excessivemanipulation of the spool of the flow rate control valve can be avoidedat the initial stage of the operation of the spool. In addition, thesudden shift of the spool of the flow rate control valve is restrictedso that the shock and the sudden operation that occur during the initialoperation of the work apparatus can be minimized.

Further, the spool of the flow rate control valve is shifted over apredetermined distance to cause the orifice 14 to be closed so that theunnecessary loss of flow rate can be prevented.

While the present invention has been described in connection with thespecific embodiments illustrated in the drawings, they are merelyillustrative, and the invention is not limited to these embodiments. Itis to be understood that various equivalent modifications and variationsof the embodiments can be made by a person having an ordinary skill inthe art without departing from the spirit and scope of the presentinvention. Therefore, the true technical scope of the present inventionshould not be defined by the above-mentioned embodiments but should bedefined by the appended claims and equivalents thereof.

1. A flow rate control valve for a construction machine comprising: avalve body including a pump path to which hydraulic fluid from ahydraulic pump is supplied, a supply path connected to the pump path,and actuator ports connected to a hydraulic actuator; a spool installedin the valve body and shifted in response to a signal pressure appliedthereto to cause the supply path and the actuator port to fluidicallycommunicate with each other selectively; a tank path installed in thevalve body and connected to a hydraulic fluid tank; and an orificeformed in the spool, the orifice including an inlet formed at an endportion to which the signal pressure is applied and an outlet formed tofluidically communicate with the tank path, wherein part of the signalpressure is discharged to the hydraulic fluid tank through the orificeat an initial stage of the operation of the spool.
 2. The flow ratecontrol valve according to claim 1, wherein the hydraulic actuatorcomprises at least one of a boom cylinder, an arm cylinder, and a bucketcylinder.
 3. The flow rate control valve according to claim 1, whereinthe outlet of the orifice is formed at a position that is spaced apartby a predetermined distance from the end portion of the spool to whichthe signal pressure is applied so that the orifice is closed after thespool is moved over a predetermined distance in response to the signalpressure applied thereto.
 4. The flow rate control valve according toclaim 1, wherein the orifice is formed at at least one of both ends ofthe spool.